I'd go with the Nikon system. You get two of the SB-R200 speedlights with the kit, and I think they are pocketable compared to the other flashes. Since they're easy to carry, you can bring one or two wherever you go that might need flash, and quickly set up a wireless flash environment by simply holding them and using the in camera commander.

I have the Nikon macro flash kit and it is really great. While at first it seems like a lot of money you really do get a lot for what you pay. I'm dead tired at the moment but I'll try to answer questions tomorrow if there are any.